1. Field of the Invention
At present the most widely spread lock inserts in the Czech Republic are lock inserts of the system FAB or its many modifications. The lock insert is rotatable, i.e. after the appropriate key is inserted, and the respective pawls arranged in a row one after another are unlocked, whereafter the appropriate liner may be rotated and entrain an operating projection for a pawl of a door lock. Such an arrangement of a door lock may be easily overcome by a specialist, especially when using sets of various lamellas. To avoid this, some of the modifications of said lock inserts are provided with two rows of pawls. Even such an arrangement does not prevent sufficiently its trespass.
By using brute force it is either possible to break out known lock inserts or to drill out a set of its blocking pawls and so on. To decrease the chance of breaking out lock inserts, different massive shields are used on the outside of the system of lock inserts. However, they form a solid hold for extending of the whole door frame.
Further improvements have been designed in the aim to secure the lock insert against breakage of its rotatable part by brute force, to make it resistant against unauthorized handling, especially against breakage and drilling out, to prevent its vulnerability to brute mechanical interference, to enhance its resistance against objects emulating keys, and to make it impossible to take unauthorized impressions of the arrangement of the inner locking system and so on.
2. Description of the Prior Art
Said aim has been achieved by a lock insert, which consists of a first locking system for axial contact with the frontal end of the key, where the first locking system is formed by a bottom of a blocking liner having an axial carrier cavity for the frontal end of the key, the liner being provided on the outside with at least one of said operating projections and in its housing with at least one radial opening for passage of a distance element, and of a second locking system for radial contact with the key, where the second locking system is formed by a hollow unrevolving liner substantially and coaxially enclosing, on the outside and on the inside, said blocking liner and which is provided with radially slidable elevation means for each distance element. The disadvantage of this solution consists in the use of a coupling system attached to the blocking liner. During opening the rotatable plate could slip, especially when the mechanism of the mortised lock is damaged or worn out.
DE-A-327 767 discloses a lock insert with a revolving operating projection for a lock pawl, whereby the lock insert comprises a first locking system for axial contact with a frontal end of a key, the first locking system being formed by a blocking liner with a bottom having an axial carrier cavity for the frontal end of the key and being provided on the outside with the operating projection, and a second locking system for radial contact with the key, the second locking system being formed by a hollow unrevolving liner coaxially enclosing from the outside the blocking liner and being provided with a radially slidable elevation means for the distance element.
The main disadvantage of this system is a complicated and demanding (from a production point of view) construction of the key, which consists of a key shank (see claim 1 of D1) and of a teeth part for setting out tumblers of the locking system, the teeth part being rotationally arranged on the key shank. Further on, as the teeth part is flat in shape, all tumblers must be arranged in one plane and all springs push the inserted key (via tumblers) in one direction. This is one of the reasons why the frontal end of the key shank must be pivotally embedded. And not only the key shank, but the teeth part as well are pivotaly mounted, which means that a cumulative tolerance of the axial coincidence of the teeth part and of the key hole is much bigger than that which is necessary in simpler keys construction. This cumulative tolerance, necessary for enabling of both rotational movements, brings about the necessity of bigger tolerance in lengths of the tumblers, ensuing into much smaller variability of keys for the locking system (ie. less combinations for the same number of tumblers and the same length-in the radial direction-of the teeth part). Another disadvantage ensuing from such a construction is a small safety against housebreakers. It is relatively easy for a housebreaker to open such a lock with a vibration means. Namely, when a housebreaker axially vibrates a key having all possible teeth, which all have maximum radial length, and at the same time tries to turn this key, the tumbler which needs the smallest height of the tooth locks in a shear plane of the lock insert. Next, the tumbler needing a bit bigger height of the tooth locks, and so on up to the tumbler with the biggest height of the tooth, and then it is possible to turn the lock insert and open the door.
AU-B-485 117 discloses a pin tumbler cylinder lock key blank, where the blade of said key blank includes a guide section extending lengthwise of said blade and following a helical path. A disadvantage of this solution is as follows: As the key is actually a blade in a helical form, the tumbler holes in the key hole are arranged on a spiral, the shape of which is given by the helical shape of the key blade. The lead of the helix has to be constant to enable the insertion of the helical key through the whole travel of the key hole. The key hole in the blocking liner thus reliably leads the housebreakers to a proper means for opening those locks. The opening of such a lock is, for a person skilled in the art, quite easy.